[sdiy] Re: Learning electronics (was Polyevolver)

[Bob Weigel]

Oops sorry..always confusion there because fusibles are also 
'flameproof' of course.  And yes don't try it on the space shuttle is 
always good advice :-).  Fusibles usually look shinier than flameproof's 
which tend to have a dull and often blue appearance btw. (Just to show 
my tired brain does know the difference :-).) -Bob

harrybissell wrote:

>Bob Weigel wrote: <snipp'd and mutilated)
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>>I wasn't thinking flameproof resistors would be likely all over a moog
>>rogue and hence the thought there :-).  Perhaps a couple in the power
>>supply.  Some mixing boards use them on each module which is a nice idea
>>to effectively fuse each section.
>>    
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>Don't confuse "Flameproof" with "Fusible" resistors.  Flameproof means they
>will not light on fire when they fail.  They can deliver SO MUCH wattage that
>they may glow cherry red and burn everything else in sight, before they open.
>
>Fusible resistors are designed to open quickly when overloaded.
>
>(I know, a manufacturer I worked for made the mistake and wondered why failed
>boards suddently looked like a barbeque !!!)
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>>btw and are often yellow
>>colored.  I can't recall what they use for dielectric in those at the
>>moment.
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>Those are usually multilayer ceramic. Terrible temperature stability, who cares
>in a bypass application (ok KD... who cares at audio frequencies anyway :^)
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>>But small caps like that all have frequency
>>response characteristics that are fine for audio and microphonic
>>characteristics and field exposure aren't usually a factor in synths.
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>small caps (like less than .001uF) are often G0G or NP0 - temperature
>stable.  Whether they suffer from the other weaknesses of caps (dielectric
>absorption, or modulation of capacitance with applied voltage) is still an issue.
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>>    But life is short...and I've substituted in many applicaitons
>>figuring that the mfg. PROBABLY selected the cap I'm seeing because they
>>got the BEST DEAL on a WAD of them :-).
>>    
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>This is the "either the engineer was stupid, or they were so clever that I don't
>even recognize how clever they really are..." issue again.  Sub away if you don't
>care, roll the dice. It will either work, or not. DON'T TRY THIS if you are on the
>
>space shuttle  :^P
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>H^) harry
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